X-ray computer tomography apparatus

Abstract

An X-ray computer tomography apparatus which performs prep scanning prior to main scanning to acquire information for use in reconstruction of a tomographic image for diagnosis, the main scanning including rotary scanning around a rotation axis, and axial scanning along the rotation axis, the X-ray computer tomography apparatus includes determination unit which determines a speed based on a change of a characteristic amount concerning information obtained by the prep scanning, and a unit which controls, to the determined speed, a speed of the axial scanning in a period from the start to the completion of the main scanning.

1. An X-ray computer tomography apparatus which performs prep scanning prior to main scanning to acquire information for use in reconstruction of a tomographic image for diagnosis, the X-ray computer tomography apparatus comprising:
 a determination unit which determines a speed based on a change of a characteristic amount concerning information obtained by the prep scanning; and 
 a unit which controls, to the determined speed, a speed of an axial scanning in a period from the start to the completion of the main scanning. 
 
   
   
     2. The X-ray computer tomography apparatus according to  claim 1 , wherein the determination unit determines the speed based on an average inclination of the change of the characteristic amount in a predetermined period. 
   
   
     3. The X-ray computer tomography apparatus according to  claim 2 , wherein the determination unit judges a velocity of blood flow based on the inclination to determine the speed based on the velocity of blood flow. 
   
   
     4. The X-ray computer tomography apparatus according to  claim 1 , further comprising:
 a unit which changes an information collecting density per unit time during the axial scanning in accordance with the determined speed. 
 
   
   
     5. The X-ray computer tomography apparatus according to  claim 1 , wherein the characteristic amount is one of an average value of a plurality of CT values obtained concerning a plurality of pixels in an interest region by the prep scanning; an added value of the plurality of CT values; an average value of difference values between the plurality of CT values and a CT value obtained from the same pixel before injecting of a contrast medium is started; and an added value of the difference values between the plurality of CT values and the CT value obtained from the same pixel before the injecting is started. 
   
   
     6. An X-ray computer tomography apparatus which performs prep scanning prior to main scanning to acquire information for use in reconstruction of a tomographic image for diagnosis, the X-ray computer tomography apparatus comprising:
 a determination unit which determines a timing to start the main scanning based on an inclination of a change of a characteristic amount with time concerning information obtained by the prep scanning; and 
 a unit which controls the X-ray computer tomography apparatus to start the main scanning at the determined timing. 
 
   
   
     7. The X-ray computer tomography apparatus according to  claim 6 , wherein the determination unit determines the timing based on an average inclination of the change of the characteristic amount in a predetermined period. 
   
   
     8. The X-ray computer tomography apparatus according to  claim 6 , wherein the determination unit judges a velocity of blood flow based on the inclination to determine the timing based on the velocity of blood flow. 
   
   
     9. The X-ray computer tomography apparatus according to  claim 6 , wherein the characteristic amount is one of an average value of a plurality of CT values obtained concerning a plurality of pixels in an interest region by the prep scanning; an added value of the plurality of CT values; an average value of difference values between the plurality of CT values and a CT value obtained from the same pixel before injecting of a contrast medium is started; and an added value of the difference values between the plurality of CT values and the CT value obtained from the same pixel before the injecting is started. 
   
   
     10. The X-ray computer tomography apparatus according to  claim 6 , further comprising:
 a unit that outputs a guidance concerning the main scanning synchronously with the start of the main scanning at the determined timing.